Many debilitating medical conditions may be alleviated by stimulating targeted nerves and muscles. For example, electric current may be applied to a nerve or bundle of nerves to disrupt signals carried by, or to affect muscles controlled by, those nerves. Common examples of neural stimulation devices include cardiac pacemakers, devices to control epilepsy and chronic pain, etc.
In conventional applications, the ability of neuromodulation systems to operate over extended periods of time is limited by the endurance of their power supplies (e.g., batteries). This approach works well for devices used for short time periods, but can be problematic for devices which must operate beyond the life span of the batteries. For such devices, additional surgery may be necessary to replace the worn batteries. Alternatively, an external power supply carried by the patient may be connected to the implanted device by wires or other connections to provide a long lasting, constant power supply. However, the wires penetrating the skin increase the likelihood of infection and other negative reactions at the location where the connections penetrate the skin.
The size of components of conventional implanted neuromodulation systems often causes discomfort and may reduce a patient's ability to carry out routine tasks. In addition, the cost of such implanted devices (e.g., implanted pulse generators) may be significant. Implanted pulse generators also have a limited life span, usually around 5 to 10 years, after which they must be replaced. As with batteries, this may involve additional surgery with the associated discomfort and costs. It may also be extremely difficult to perform upgrades or repairs to conventional, implanted pulse generators due to the same concerns described above.